The present invention relates to a motor vehicle actuating unit including a master cylinder which is attached to a wall in the motor vehicle.
In particular in crashes which cause deformations to the front part of the motor vehicle, there is the risk that parts which are positioned in this area, in particular the actuating unit of the hydraulic brake system located at the splashboard, will reduce the space available directly in front of the driver so that injuries are imminent. Therefore, German patent No. 43 04 565, for example, discloses the provision of means which simulate increased fluid requirements of the brake system in a crash with deformations at the front part of the motor vehicle and, thus, permit extending the actuating travel of the actuating unit. Hydraulic valves are provided in this arrangement which must be operated in the case of a crash to achieve the desired effect.
A disadvantage of this known arrangement is that relatively high demands must be placed on the valves because they must function correctly and quickly in the case of a crash, but remain unoperated in the normal case, usually for years.